1. Field of the Invention
The present invention relates to a substrate for an ink jet recording head, a recording head using the substrate, a recording apparatus with the recording head, and a method of driving the recording head.
2. Related Background Art
Nowadays, various recording methods have been developed and are available. Of these methods, ink jet recording methods for performing recording by emitting an ink from emission ports in accordance with a recording signal are popularly used since the apparatus used in these methods can be easily rendered compact and generates low noise. Among these methods, a method using electro-thermal energy conversion elements for applying heat to an ink to cause a bubble forming phenomenon as emission energy generation elements for emitting an ink is preferably used.
An ink jet recording head of this type has an element substrate on which first resistor elements (ink emission resistor elements) as electro-thermal energy conversion elements, which are electrically connected to a function element for selectively driving a plurality of electro-thermal energy conversion elements for emitting an ink, as described above, and second resistor elements (temperature control resistor elements), which are arranged for adjusting the viscosity of the ink by controlling the temperature, and are not electrically connected to the function element, are formed.
When the resistance values of the first resistor elements formed on the element substrate suffer a variation in the manufacture, if a common driving If voltage is applied to the respective heads, different amounts of heat are generated due to a variation in resistance value, resulting in different ink bubble forming phenomena. Thus, ink emission amounts become nonuniform in units of heads, or stable ink emission cannot often be attained. Therefore, the resistance values of the emission resistor elements of the respective heads must be measured by some method, and voltages corresponding to the measured resistance values must be applied to suppress emission amount nonuniformity. However, when the resistance value of the emission resistor element of each head is to be directly measured, a resistance value including the resistance value of the emission resistor element and that of the function element electrically connected thereto is undesirably measured. As a result, the resistance value of only the emission resistor element cannot be accurately measured.
For this reason, the present inventors measured the resistance value of the temperature control resistor element which was electrically independent from the function element formed in a similar manner to that of the emission resistor element, and calculated a sheet resistance value based on the measured resistance value of the temperature control resistor element, thus estimating the resistance value of the emission resistor element.
On the basis of the estimated resistance value, data for setting an appropriate driving signal for stable emission of an ink is stored as, e.g., 4-bit data in a memory circuit on a printed circuit board on a recording head. When the recording head which stores data of the driving electric power is mounted on a recording apparatus, a control circuit unit of the ink jet recording apparatus reads data stored in the recording head, and supplies a driving signal suited for driving the emission resistor elements to the recording head in accordance with the read data, thus achieving adjustment of ink emission in units of heads.
However, the above-mentioned temperature control resistor element has a resistance value smaller than that of the emission resistor element since it has a resistor shape satisfying L1/W1 greater than L2/W2, W1 less than W2, and L1 less than L2 (W1 and L1 are respectively the width and length of the emission resistor element, and W2 and L2 are respectively the width and length of the temperature control resistor element), so as not to form a bubble in an ink upon driving of the temperature control resistor element.
As described above, since the resistance value of the temperature control resistor element is set to be lower than that of the emission resistor element, when the resistance value is measured using the temperature control element, it is difficult to sufficiently accurately estimate the resistance value of the emission resistor element, and hence, it is difficult to drive the head by applying an appropriate driving signal to the emission resistor element.
On the other hand, when data for setting an appropriate driving signal condition for stable emission of an ink is stored in, e.g., the memory circuit on the printed circuit board on the basis of the resistance value estimated from the temperature control resistor, as described above, the number of data to be able to be stored is limited to several bits (e.g., 4 bits) in terms of a space for arranging the memory circuit. For this reason, the setting range of driving electric power to be applied to the emission resistor element is undesirably widened. In such a case, it is difficult to supply an appropriate driving signal to the emission resistor element. In order to solve this problem and to store a larger number of storage data, a memory element (e.g., a ROM or the like) may be mounted on the printed circuit board, or a region for arranging the memory circuit may be widened. However, this results in an increase in cost or size of the recording head itself.
When an appropriate driving signal cannot be set for the ink emission resistor element, e.g., when a driving signal is set to be too low, ink emission becomes unstable, and the dot size of an ink droplet diminishes, resulting in deterioration of print quality. On the other hand, when driving electric power is set to be too high, since electric power exceeding required power is supplied to the emission resistor element, the service life of the emission resistor element is shortened, and reliability of the recording head is lowered, thus posing problems to be solved.
The present invention has been made to solve the above-mentioned problems, and a representative means for solving the problems according to the present invention is a substrate for a thermal recording head, comprising a plurality of heating resistor elements for performing recording by generating heat, a plurality of wiring electrodes for supplying driving signals to the heating resistor elements, a function element, electrically connected to the heating resistor elements, for selectively driving the plurality of heating resistor elements, and a measurement resistor element which is electrically independent from the heating resistor elements and the function element, and has a resistance value larger than that of each heating resistor element,
an ink jet recording head comprising emission ports for emitting an ink, ink channels for guiding the ink to positions near the emission ports, and a substrate provided with heating resistor elements used for emitting the ink from the emission ports by applying heat to the ink, a plurality of wiring electrodes for supplying driving signals to the heating resistor elements, a function element, electrically connected to the heating resistor elements, for selectively driving the plurality of resistor elements, and a measurement resistor element which is electrically independent from the heating resistor elements and the function element, and has a resistance value larger than that of each heating resistor element,
an ink jet recording apparatus which can detachably mount an ink jet recording head comprising: a substrate provided with heating resistor elements for emitting an ink from emission ports by applying heat to the ink, a plurality of wiring electrodes for supplying driving signals to the heating resistor elements, a function element, electrically connected to the heating resistor elements, for selectively driving the plurality of resistor elements, and a measurement resistor element which is electrically independent from the heating resistor elements and the function element, and has a resistance value larger than that of each heating resistor element; emission ports for emitting an ink; and ink channels for guiding the ink to positions near emission ports, and which comprises a control circuit for electrically measuring a value based on the resistance value of the measurement resistor element of the mounted recording head, and setting a condition of a driving signal for driving the heating resistor elements on the basis of the measured resistance value, or
a method of driving a recording head, comprising the step of electrically measuring a value based on a resistance value of a measurement resistor element arranged in a recording head for performing recording based on heat generated by heating resistor elements, the step of setting a driving signal to be applied to the heating resistor elements on the basis of the measured value, and the step of applying the set driving signal to the heating resistor elements of the recording head.